Temporary pacing is indicated in patients with new AV or BBB in the setting of acute bacterial endocarditis. The development of a new conduction system abnormality generally suggests that there is a perivalvular (ring) abscess that has extended to involve the conduction system near the AV node and/or the His bundle. The endocarditis generally involves the non-coronary cusp of the aortic valve. In one study, high-grade or complete heart block developed in 22% of patients with aortic valve endocarditis and new first-degree AV block.56 Although these studies are retrospective, the patient with development of new AV block or BBB, especially in the setting of aortic valve endocarditis, should probably undergo temporary pacing while cardiac evaluation continues.
Treatment of tumors of the head and/or neck or around the carotid sinus may in some circumstances give rise to high-grade AV block. Temporary pacing may be required during surgical treatment, radiation therapy, or chemotherapy. If the tumor responds poorly, permanent pacing may be necessary in some cases. The long-term risk for subsequent heart block due to tumor recurrence is difficult to predict in some cases.
Lyme disease, a tickborne spirochete infection, causes a systemic infection with arthritis, skin lesions, myalgias, meningoencephalitis, and cardiac involvement in 5% to 10% of patients.57 Lyme disease is epidemic in the summer months in the northeastern United States. Carditis typically occurs relatively late in the course of the illness, usually 4 to 8 weeks after the onset of symptoms. AV block is the most common manifestation of carditis and tends to be transient. Block is most common at the level of the AV node and fluctuation between first-degree and higher degrees of AV block is frequent. Temporary cardiac pacing may be required, but the conduction disturbances usually resolve spontaneously, especially with antibiotic treatment, so permanent cardiac pacing rarely is necessary. Similar conduction disturbances can occasionally be seen in patients with viral myocarditis, as well as with other tickborne infections.
A number of medications may produce transient bradycardia that may require temporary pacing until the drug has been stopped (see Box 1.2). These drugs may cause sinus node dysfunction and/or AV block; if used in combination, their effects may become more potent and exacerbate mild or latent conduction system disease. If long-term therapy with these agents is necessary for an underlying disorder and a substitute cannot be found, permanent pacing may be required.
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